Walter Michael Miller, Jr. is primarily remembered today for his award-winning novel, A Canticle for Leibowitz, the only novel of his that was published during his lifetime. Prior to its publication, however, Miller was the author of several excellent science fiction stories. His first professional sale was "MacDougal's Wife," to American Mercury in 1950; and his first SF sale was "Secret of the Death Dome" in Amazing (January, 1951 issue). During the early 1950s he also wrote scripts for television's "Captain Video and His Video Rangers."

Miller was born in New Smyrna Beach, Florida, and was educated at The University of Tennessee and The University of Texas at Austin. Before becoming a full-time writer, he worked as an engineer. During World War II he served in the Army Air Corps as a radioman and tail gunner, flying 53 bombing missions over Italy. He took part in the bombing of the Benedictine Abbey at Monte Cassino, an event that haunted him for the rest of his life.

After the War, Miller converted to Catholicism. He married Anna Louise Becker in 1945, and they had three daughters and one son. In 1953 he lived with SF writer/editor Judith Merril for six months. Miller began writing while recovering from an automobile accident. Between 1951 and 1957, he published over three dozen SF stories, winning the Hugo Award in 1955 for "The Darfsteller." Late in the 1950s Miller assembled a novel from three closely related novellas he had published in The Magazine of Fantasy & Science Fiction (in 1955, 1956, and 1957, respectively). This fix-up novel was titled A Canticle for Leibowitz, and was published in 1959. At the time of its publication, reviews were mixed.

Canticle is a post-holocaust story revolving around the canonization of a fictional Saint Leibowitz and is now considered a masterpiece of the genre. It won the 1961 Hugo Award for best novel. Canticle is also a statement about the cycles of world history and Roman Catholicism as a force of stability during history's dark times. After the success of Canticle, Miller never published another new story in his lifetime, although several compilations of his earlier stories were issued in the 1960s and 1970s. In addition, a radio adaptation of Canticle was produced by WHA Radio and NPR in 1981 and is available on CD. Genre critic David Pringle called Canticle "the greatest of all post-bomb stories."

In MIller's later years he became a recluse, avoiding contact with nearly everyone, including family members. According to Terry Bisson, Miller struggled with depression during his later years, but had managed to write a 600-page manuscript for the sequel to Canticle before taking his own life with a gun in January, 1996. The sequel, titled Saint Leibowitz and the Wild Horse Woman, was completed by Bisson and published in 1997.